Deep learning is a type of machine learning and can perform characterization learning on data. Deep learning can obtain features by using unsupervised or semi-supervised feature learning and a stratified feature extraction algorithm. A basic structure of deep learning is a deep learning neural network. The deep learning neural network is an artificial neural network with at least one hidden layer, and can form abstract high-level features representing attribute categories by combining lower-level features, so as to find distributed representations of data.